Method for detecting phase change temperatures of molten metal

ABSTRACT

A detection device for molten metal is provided. The detection device includes a sample cup having a cavity configured to receive a sample of molten metal and a blob arranged in the cavity. The blob includes a carbide stabilizing element and a hydrogen releasing material including a hydroxide of an alkaline earth metal. The blob is provided for use in detecting phase change temperatures during solidification of a sample of molten cast iron. The blob is also resistant to moisture gain and moisture loss during transport and storage. A method of detecting phase change temperatures of the molten iron or molten cast iron sample using the blob and a method of manufacturing the blob are also provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of co-pending U.S. patent applicationSer. No. 13/677,808, filed Nov. 15, 2012, the disclosure of which isincorporated herein by reference.

BACKGROUND OF THE INVENTION

The invention relates to a detection device for metal melts, inparticular molten iron. The device has a sample cup and a blobcontaining a carbide stabilizer and a hydrogen releasing material isarranged in the sample cup.

During the processing and preparation of molten metal, particularlymolten iron, it is desirous to monitor certain chemical constituents ofthe metal. One common means for doing so is the use of disposable phasechange detection devices, which measure the temperature of a sample ofthe molten cast iron during solidification in order to detect thetemperatures of the phase changes. Such phase change detection devicestypically comprise a mold body having a cup-like shape and an upper openend for receiving a sample of molten metal. The devices also typicallyinclude a thermocouple extending into the cup below the surface of theas-poured molten metal sample. One such conventional phase changedetection device is described in U.S. Pat. No. 3,267,732.

Typically, an operator scoops a sample of molten metal from a batch ofthe molten metal using a small spoon or ladle, and then pours the sampleof molten metal into the sample mold of a detection device. Thethermocouple continuously records the temperature of the metal as itsolidifies. From the phase change temperature measurements of thesolidifying metal sample, certain properties and aspects of the chemicalcomposition of the cast iron sample, such as, but not limited to, carboncontent, silicon content, and degree of saturation or carbon equivalentlevel, may be predicted. The operator can then utilize this informationto make any necessary adjustments to the molten metal bath beforecasting.

In certain circumstances, such as for hypercutectic irons, it is usefulto achieve a graphite-free, white solidification of the sampled iron.The term “white solidification” is a common term in the art and refersto an as-cast structure dominated by the solidification of iron in acarbide phase that, when fractured, appears “white.”

U.S. Pat. No. 3,546,921 (“the '921 patent”) teaches that the addition tothe molten iron of a pellet comprising a carbide stabilizing element orcompounds of such elements will promote the white solidification.However, the '921 patent does not achieve optimal white solidificationbecause the pellet tends to rise to the surface of the molten metal as aslag, or tends to burn in atmospheric oxidation, such that it is notavailable for white solidification. Further, if the molten iron has afairly high carbon content or if the molten metal has been heavilyinoculated, the likelihood of achieving a total white solidificationbased on the pellet addition of the '921 patent is low.

U.S. Pat. No. 4,003,425 discloses that coating the inside of the samplemold with a material containing water to be liberated at the temperatureof the molten iron, will improve the effectiveness of the aforementionedcarbide promoting additives. In this instance, water is a vehicle whosepurpose was to make available hydrogen to alloy with the metal. Theimprovement of an iron, especially hypereutectic irons, to solidify in awhite structure is promoted by the presence of hydrogen.

U.S. Pat. No. 4,029,140 (“the '140 patent”) adopts this type of coatingfor use in promoting the carbide reaction in a disposable sample cup.The coating contains a carbide stabilizing element or compound and amaterial containing loosely combined water or some hydroxyl groups. Thewater or hydroxyl groups are retained after drying the coating, but arefreely liberated from the coating at the temperature of the moltenmetal.

However, the method of applying the coating of the '140 patent to suchconventional disposable phase change devices was limited in itsusefulness, because both the walls of the sample cup and thethermocouple itself were coated. As a result, these conventional devicessuffered from a thermal lag in the thermocouple. U.S. Pat. No. 4,274,284purports to eliminate the thermal lag by the addition of an ablativecoating which ensures that the thermocouple junction is exposed to themolten metal when the sample is poured into the device.

However, the multiple coatings negated the purported economical benefitof the '140 patent. In addition, the above-described coatings wereapplied were to be thin, which was found to be a major drawback.Specifically, it was found that the conventional coated sample cupscannot be completely filled with molten iron due to the violent releaseof hydrogen from the thin coating and due to the carbide promotingmaterial rapidly boiling away from the thin coating, rather thanalloying with the metal. As such, the volume of metal remaining in thesample cup was insufficient for obtaining temperature measurements. Inturn, the amount of carbide stabilizing additives to be added to themolten metal in order to effectively promote white solidification couldnot be reliably predicted.

Further, the carbide promoting materials and the hydrogen releasingsubstances of the above-described prior art coatings have melting pointsbelow that of iron and boiling points near the temperature of the phasechanges that are to be monitored. Thus, even with extreme care, areaction of the coating materials with the molten metal is to beexpected, and the extent of this reaction is of importance providing acontrolled alloying of the additives.

Instead of a paint or coating, U.S. Pat. No. 4,059,996 discloses a blobof material which is fixed to the bottom of the sample cup. The blob ofmaterial includes a carbide formation promoting material, a refractorymaterial and a material for evolving hydrogen (i.e., water glass) uponcontact with the molten metal. The refractory material aids inpreventing the carbide formation promoting material from being burned upquickly and mixing too quickly with the molten metal. The blob isinitially in the form of a fluid mixture that is deposited in the samplecup, and is then dried to a solid in an oven.

U.S. Pat. No. 4,515,485 (“the '485 patent”) also discloses the use of ablob of material. However, the blob is disposed in a recess of a bottomwall of the sample cup, so that the surface area of the blob exposed tothe molten metal is limited, and thus the amount of hydrated materialexposed to the molten metal is limited.

None of the above-described prior art coatings and blobs satisfactorilyachieves optimal white solidification for all compositions of castingirons. The reason for this failure is that each of the above-discussedprior art devices and methods fails to recognize and appreciate theproblem of the environmental instability of the materials of thecoatings and blobs. Specifically, the present inventors have found thatthe materials utilized in the above-discussed prior art coatings andblobs will, over time, lose moisture to or absorb moisture from thesurrounding environment, during storage and transport to the location ofuse and also while awaiting use after delivery to the location of use.

For example, the prior art detection devices are provided with thecoating or blob at the time of manufacturing of the device, well inadvance of the time when these devices will actually be used. Themanufactured devices are then boxed, palletized, shrink-wrapped andtransported by land, sea or air to be unwrapped and used in anotherenvironment or location. However, during this time, the detectiondevices are typically subjected to uncontrolled transport and storageenvironments. In addition, the location at which the detection device isultimately unwrapped and used may also be under conditions of extremesof temperature and humidity.

The present inventors have thus found that the prior art detectiondevices, and particularly the hydrogen releasing capacity of thecoatings and blobs of these devices, are unstable because the coating orblob materials are susceptible to changes in their hydration levels.Specifically, the coatings or blobs are susceptible to taking onadditional hydration in a moist environment and losing hydration in asufficiently dry environment.

Although loss of moisture over time is problematic, the presentinventors have found that exposure to damp conditions is essentiallydetrimental for the prior art coatings and blobs. Specifically, in dampconditions, where the prior art coatings and blobs are susceptible touncontrolled moisture absorption from the surrounding damp environment,uncontrolled boiling of the molten metal sample results. Accordingly, asdescribed above, the volume of metal remaining in the sample cup isinsufficient for obtaining temperature measurements and, in turn, thepredictability of the carbide stabilizing additives of the prior artcoatings and blobs is negatively impacted.

The '485 patent recognizes that uncontrolled boiling leads to changes inthe amount of molten metal remaining in the sample cup duringsolidification, which thus produces different results when the blobs areof a uniform size. However, this prior art device does notsatisfactorily eliminate or reduce boiling. Thus, the device of the '485patent fails to recognize the problem newly discovered by the presentinventors, namely that the occurrence of uncontrolled boiling isactually the result of absorbed moisture in the carbide promotingmaterials. Indeed, the present inventors found that some environmentallyabsorbed water inevitably accumulates on even the limited exposedsurface area of the blob of the '485 patent. As a result, excess boilingstill occurs, thereby failing to yield the desired improvement.

Thus, the above-discussed prior art devices and methods all fail torecognize the existence of dampness and fail to address how to preventdamp conditions which occur as a result of the environmental exposure ofthe coatings or blobs.

BRIEF SUMMARY OF THE INVENTION

An objective of the present invention is to provide a sampling deviceincluding a blob which is capable of resisting changes in its hydrogenreleasing capacity due to moisture absorption from environmentalexposure during long term periods of shipping and storage.

Another objective of the present invention is to provide a samplingdevice in which metal samples can be obtained with optimal whitesolidification, while limiting the amount of hydrogen that must be addedto the samples and thus limiting the violent reaction of the materialdirectly exposed to the molten metal.

These objectives are achieved by embodiments of the present inventiondescribed and claimed in the following.

One aspect of the present invention is directed to a sampling device formolten metal. The sampling device comprises a sample cup having a cavityconfigured to receive a sample of molten metal and a blob arranged inthe cavity. The blob comprises a carbide stabilizing element and ahydrogen releasing material including a hydroxide of an alkaline earthmetal.

Another aspect of the present invention is directed to a blob for use indetecting phase change temperatures of a sample of molten iron or moltencast iron. The blob comprises a carbide stabilizing element, magnesiumhydroxide as a hydrogen releasing material, a retardant which resistsreaction of the blob upon contact with a sample of molten iron or moltencast iron, and a binder.

In another embodiment, the blob comprises tellurium in an amount of 15%to 60% by weight based on a total weight of the blob and magnesiumhydroxide in an amount of 40% to 85% by weight based on the total weightof the blob. The blob is resistant to moisture gain and moisture lossduring transport and storage.

Another aspect of the present invention is directed to a method ofdetecting phase change temperatures of a sample of molten iron or moltencast iron. The method comprises the steps of: providing a detectiondevice including a temperature sensor and a sample cup with a cavityconfigured to receive a sample of molten iron or molten cast iron;arranging a blob in the cavity; depositing a sample of molten iron ormolten cast iron into the cavity, and allowing the molten iron or moltencast iron sample to solidify while simultaneously measuring phase changetemperatures of the solidifying sample. The blob comprises a carbidestabilizer and magnesium hydroxide as a hydrogen releasing material. Theblob reacts upon contact with the molten iron or molten cast ironsample, such that hydrogen is released from the magnesium hydroxide intothe molten iron or molten cast iron sample.

Another aspect of the present invention is directed to a method ofmanufacturing a blob for use in detecting phase change temperatures of asample of molten metal. The method comprises: forming a fluid blobmixture comprising a carbide stabilizer and magnesium hydroxide as ahydrogen releasing material; providing a detection device including asample cup with a cavity configured to receive a sample of molten metal;depositing the fluid blob mixture into the cavity; and drying the fluidblob mixture to form a blob.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The foregoing summary, as well as the following detailed description ofthe invention, will be better understood when read in conjunction withthe appended drawings. For the purpose of illustrating the invention,there are shown in the drawings embodiments which are presentlypreferred. It should be understood, however, that the invention is notlimited to the precise arrangements and instrumentalities shown. In thedrawings:

FIG. 1 is a side elevation view in cross section of a detection deviceaccording to an embodiment of the invention; and

FIG. 2 is a top plan view the detection device shown in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a detection device for molten metals.More particularly, the present invention relates to a device fordetecting and recording the temperatures of phase changes of a sample ofmolten iron during cooling and solidification of the molten iron. Thepresent invention also relates to a blob of material to be attached toand positioned within the detection device.

Since the blob of material of the present invention may be applied toconventional detection devices, the structure and materials ofconstruction of a typical detection device will be described withreference to FIGS. 1-2. However, it will be understood by those skilledin the art that the blob of material of the present invention may alsobe utilized with or in detection devices having other structures andmaterials of construction.

Referring to FIGS. 1-2, there is shown a detection device 10. Thedetection device 10 is preferably a disposable device and is used forsamples of molten metal at temperatures of 1,150° C. to 1,450° C., andmore preferably for samples of molten iron or molten cast iron attemperatures of 1,250° C. to 1,350° C. The detection device 10 comprisesa sample chamber or cup 12 made from a refractory material. For example,the sample cup 12 may be preferably made from molded foundry sand,refractory cement, or a combination of these materials. More preferably,the sample cup 12 is made from a molded thermosetting resin coated sand.Most preferably, the sample cup 12 is made from a molded phenolic resincoated sand. However, it will be appreciated by those skilled in the artthat the sample cup 12 may be made from any material capable ofresisting the temperature of the molten iron and which does notadversely interfere with the desired diction and measurement.

The sample cup 12 preferably has a generally square or rectangularcross-sectional shape with an upper open end 14 and a closed bottom wall16. A cavity 18 is formed and defined between the upper end 14 and thebottom wall 16 of the sample cup 12. The cavity 18 has a generallycylindrical configuration. The underside of the bottom wall 16 includesa centrally disposed recess 20 between opposing walls 22, 24 of thesample cup 12.

The sample cup 12 includes a temperature sensor 25 for sensing thetemperature of the molten metal sample contained therein and forfacilitating recording of all temperature changes. The temperaturesensor includes a protective tube 28 which is preferably made of quartz.However, it will be understood by those skilled in the art that otherconventional materials of a similar nature to quartz may alternativelybe utilized. The protective tube 28 is preferably annular in crosssection and transparent to radiation.

Thermocouple wires 30, 32 are at least partially disposed within theprotective tube 28. The protective tube 28 extends across the cavity 18and its ends are supported by first and second aligned bores 26 formedin oppositely disposed walls of the sample cup 12. The bores 26 aresubstantially closed with a refractory cement 33 that seals the bores 26and maintains the position of the temperature sensor. The bores 26 arepreferably provided in a location so that their axis will lie along acentral lateral axis L1 of the cavity 18.

The thermocouple wires 30, 32 of the temperature sensor may be any oneof the conventional thermocouple materials utilized heretofore inconnection with disposable thermocouples, such as chromel and alumel,which are used with hypereutectic cast iron samples (i.e., a Type Kthermocouple). Juxtaposed ends of the thermocouple wires 30, 32 arejoined together at a hot junction 34. The hot junction 34 is preferablypositioned adjacent to a central elevation axis L2 of the cavity 18.

Opposite walls 22, 24 of the sample cup 12 are provided with peripheral,vertically-extending grooves 36, 38. The first thermocouple wire 30extends through and along the first groove 36 and is bent along wall 22toward the recess 20 where it may be utilized as a contact portion for atemperature measurement recordation device (see FIG. 1). The secondthermocouple wire 32 extends along and through the second groove 38 andis bent along wall 24 toward the recess 20 where it may be utilized asanother contact portion (see FIG. 1). In one embodiment, the firstand/or second thermocouple wire 30, 32 is preferably provided with aninsulating sleeve (not shown) between the bore 26 and the bottom of thesample cup 12 to prevent an electrical connection between thethermocouple wires 30, 32 through the gases of combustion emitting fromthe body of the sample cup 12.

Again, the above-described embodiment of the sample cup 12 is forillustrative purposes only. The blob of the present invention, asdescribed in detail below, may be utilized in any one of a wide varietyof different commercially available cups used as sample cups phasechange detection devices.

Specifically, in one embodiment of the present invention, a blob 40 ispositioned within and preferably attached to the cavity 18 of the samplecup 12. The blob 40 is essentially a mass of material which ispositioned within the cavity 18. In one embodiment, the blob 40 ispreferably adhered to at least one interior wall of sample cup 12, andmore preferably to a top side of the bottom wall 16 of the sample cup12, by action of the binder component of the blob 40.

The blob 40 according to the invention comprises two essentialcomponents: a carbide stabilizing element and a hydrogen source. Theblob 40 may also optionally comprise a retardant, a binder and/or adispersant. The properties and role of each of these components isdescribed hereinafter in greater detail. The blob 40 is preferablyessentially devoid of any hygroscopic materials, as such materials havean affinity for atmospheric moisture and thus tend to become damp whenexposed to moist air and humid environments.

In one embodiment, the blob 40 is formed by mixing the components of theblob 40 together, depositing the resulting fluid blob mixture withconventional fluid dispensing equipment into the cavity 18 of the samplecup 12, and then drying the fluid blob mixture to obtain the blob 40.

The volume of the fluid blob mixture is preferably 1.89% to 2.70% of thevolume of the molten iron or molten cast iron sample contained in thecavity 18 of the sample cup 12. More preferably, the volume of the fluidblob mixture is 2.00% to 2.30% of the volume of the molten iron ormolten cast iron sample. Most preferably, the volume of the fluid blobmixture is approximately 2.25% of the volume of the molten iron ormolten cast iron sample. The weight of the fluid blob mixture ispreferably 0.50% to 0.85% of the weight of the molten iron or moltencast iron sample. More preferably, the weight of the fluid blob mixtureis 0.60% to 0.80% of the weight of the molten iron or molten cast ironsample. Most preferably, the weight of the fluid blob mixture isapproximately 0.80% of the weight of the molten iron or molten cast ironsample

For example, for a sample cup 12 having a cavity volume of 37milliliters, if the cavity 18 is completely filled by a sample of molteniron or molten cast iron, the weight of the molten metal sample is 270grams. For such a sample cup 12, assuming that the cavity 18 will becompletely filled with a sample of molten iron or molten cast iron, thevolume of the fluid blob mixture to be dispensed in the cavity 18 ispreferably between 0.7 milliliters and 1 milliliter and the weight ofthe fluid blob mixture is preferably between 1.5 and 1.7 grams. Morepreferably, again assuming the cavity 18 will be completely filled witha sample of molten iron or molten cast iron, the volume and weight ofthe fluid blob mixture are approximately 0.85 milliliters andapproximately 1.58 grams, respectively.

After drying, the weight of the blob 40 is preferably 0.35% to 0.45% ofthe weight of the molten iron or molten cast iron sample. Morepreferably, the weight of the blob 40 is approximately 0.40% of theweight of the molten iron or molten cast iron sample.

It will be understood by those skilled in the art that the descriptionof a sample cup with a cavity volume of 37 milliliters is forillustrative purposes only. Sample cups having other cavity volumes maybe utilized, and thus the blob may be used with molten metal samples ofvarious weights and volumes. As such, it will be understood that,depending on the sample cup being used, the weight and volume of thefluid blob mixture (and thus the volume and weight of the blob 40) willbe adjusted accordingly in order to maintain the desired volume andweight percents.

Each component of the blob 40 will now be described in more detail. Itwill be understood that the phrase “wet weight,” as used hereinafter,refers to a state of the blob 40 prior to drying, in which the blobexists as a fluid blob mixture. It will also be understood that thephrase “dry weight,” as used hereinafter, refers to a state of the blob40 after drying of the fluid blob mixture to form a solid, dried blob.

The carbide stabilizing element or carbide stabilizer promotes carbideformation (i.e., white solidification) of the molten iron samplecontained in the cavity 18 of the sample cup 12. More particularly, thecarbide stabilizer is a metallic material which prevents theprecipitation of graphite in the solidifying sample. Upon contact withthe molten iron, the blob 40 reacts with the molten iron sample and thecarbide stabilizer is released from the blob 40 into the molten ironsample. The carbide stabilizer may preferably be any one of bismuth,boron, tellurium, selenium or compounds or alloys of these elements.Most preferably, the carbide stabilizer is tellurium.

In a preferred embodiment, the carbide stabilizer is present in the formof a powder having an average particle size of 5 to 100 μm. Morepreferably, the carbide stabilizer is present in the form of a powderhaving an average particle size of 15 to 50 μm. Most preferably, thecarbide stabilizer is present in the form of a powder having an averageparticle size of approximately 20 μm. Unless otherwise indicated herein,all particle sizes stated herein are d₅₀ particle diameters measured bya laser diffraction analyzer or a sedigraph which determines particlesize by sedimentation analysis. As well understood by those in the art,the d₅₀ diameter represents the size at which half of the individualparticles (by weight) are smaller than the specified diameter.

The carbide stabilizer is preferably present in an amount of 5% to 25%by weight based on the total wet weight of the fluid blob mixture and inan amount of 7% to 37% by weight based on the total dry weight of theblob 40. More preferably, the carbide stabilizer is present in an amountof 10% to 20% by weight based on the total wet weight of the fluid blobmixture and in an amount of 15% to 25% by weight based on the total dryweight of the blob 40. Most preferably, the carbide stabilizer ispresent in an amount of 12% to 14% by weight based on the total wetweight of the fluid blob mixture and in an amount of 18% to 20% byweight based on the total dry weight of the blob 40.

The hydrogen source (i.e., hydrogen releasing material) is a materialwhich evolves into or releases hydrogen to the molten metal, when theblob 40 is contacted by and reacts with the sample of molten metal,particularly molten iron, contained in the sample cup 12.

The hydrogen releasing material is preferably a material having one ormore ionic bonded hydroxide groups, as such a material is resistant tomoisture gains and losses and, thus, will maintain its level ofhydration in moist or dry transport, storage and use conditions orenvironments. More preferably, the hydrogen releasing material is onethat does not absorb moisture. The hydrogen releasing material is alsopreferably a material which is stable at the drying temperature for theblob 40, but which decomposes at the temperature of use of the detectiondevice 10.

Preferably, the hydrogen releasing material is a hydroxide of analkaline earth metal. More preferably, the hydrogen releasing materialis one of magnesium hydroxide, tellurium hydroxide, calcium hydroxide,and bismuth hydroxide. Most preferably, the hydrogen releasing materialis magnesium hydroxide. As such, upon contact and reaction of the blob40 with the molten iron sample, magnesium is released from the magnesiumhydroxide into the molten iron sample.

Magnesium would conventionally not have been used in a detection devicedesigned to promote white iron solidification, because the meltingtemperature of magnesium is below that of the molten iron, and thuswould be expected to alloy into the molten iron and interfere with andcounteract the action of the carbide stabilizing element (e.g.,tellurium). However, the present inventors have discovered thatmagnesium can surprisingly be used in a detection device for white ironsolidification, because when the magnesium is in the presence of anoxygen containing material that will decompose, releasing an equal orgreater stoichiometric proportion of oxygen, the released magnesium iscompletely neutralized by oxidation prior to any contamination of themolten metal or interference with the tellurium.

The hydrogen releasing material is preferably present in an amount of10% to 37% by weight based on the total wet weight of the fluid blobmixture and in an amount of 15% to 54% by weight based on the total dryweight of the blob 40. More preferably, the hydrogen releasing materialis present in an amount of 12% to 25% by weight based on the total wetweight of the fluid blob mixture and in an amount of 20% to 30% byweight based on the total dry weight of the blob 40. Most preferably,the hydrogen releasing material is present in an amount of 16% to 18% byweight based on the total wet weight of the fluid blob mixture and in anamount of 23% to 25% by weight based on the total dry weight of the blob40.

In preferred embodiments, the blob 40 also includes a retardant. Theretardant is a filler material added to the blob 40 to provide asufficiently bonded mass that remains substantially intact duringsolidification of the molten metal sample, such that release of thecarbide stabilizer and the release of hydrogen from the hydrogenreleasing material (both in vapor form) are delayed upon contact of theblob 40 with the sampled molten metal. More particularly, the retardantis a material which resists reaction and total decomposition of the blob40 upon contact with the sampled molten metal. Preferably, the retardantis a non-hydrating and refractory (e.g., ceramic) filler material.Preferred examples of the retardant include silica, calcium silicate,magnesium silicate, zirconia, alumina, and compounds thereof. Morepreferably, the retardant is an alumina silicate, and most preferably,calcined kaolin.

The retardant is preferably present in an amount of 18% to 48% by weightbased on the total wet weight of the fluid blob mixture and in an amountof 27% to 71% by weight based on the total dry weight of the blob 40.More preferably, the retardant is present in an amount of 30% to 40% byweight based on the total wet weight of the fluid blob mixture and in anamount of 50% to 60% by weight based on the total dry weight of the blob40. Most preferably, the retardant is present in an amount of 37% to 39%by weight based on the total wet weight of the fluid blob mixture and inan amount of 54% to 56% by weight based on the total dry weight of theblob 40.

In preferred embodiments, the blob 40 also includes a binder suited forhigh temperature applications. Preferably, the binder is a thermosettingbinder. More preferably, the binder is a non-hygroscopic andnon-formaldehyde thermoplastic binder. In one embodiment, the binder isa solution comprising water and a polymerized material, such aspolyvinyl alcohol, polyvinyl acetate, polyvinyl butyral and otherpolyvinyl resins, polystyrene resins, acrylic and methacrylic acid esterresins, polyisobutylene, polyamides and silicones. Most preferably, thebinder comprises a partially hydrolyzed polyvinyl alcohol solution.

The binder is preferably present in an amount of 27% to 37% by weightbased on the total wet weight of the fluid blob mixture and in an amountof 1% to 4% by weight based on the total dry weight of the blob 40. Morepreferably, the binder is present in an amount of 30% to 35% by weightbased on the total wet weight of the fluid blob mixture and in an amountof 1% to 3% by weight based on the total dry weight of the blob 40. Mostpreferably, the binder is present in an amount of 31% to 33% by weightbased on the total wet weight of the fluid blob mixture and in an amountof 1.5% to 2.5% by weight based on the total dry weight of the blob 40.

In preferred embodiments, the blob 40 also includes a dispersant. Thedispersant is a material which maintains the dispersed particles of thevarious components in suspension to prevent settling of these particles.Thus, while the inclusion of a dispersant is not necessary, doing so hasbeen found to be beneficial for manufacturing of the blob 40 on acommercial scale. Preferred examples of the dispersant include trisodiumcitrate, ammonium citrate and like materials having similar propertiesthereto. Most preferably, the dispersant is trisodium citrate.

The dispersant is preferably present in an amount of 0.04% to 1.3% byweight based on the total wet weight of the fluid blob mixture and in anamount of 0.06% to 2% by weight based on the total dry weight of theblob 40. More preferably, the dispersant is present in an amount of0.08% to 1% by weight based on the total wet weight of the fluid blobmixture and in an amount of 0.1% to 1% by weight based on the total dryweight of the blob 40. Most preferably, the dispersant is present in anamount of 0.1% to 0.5% by weight based on the total wet weight of thefluid blob mixture and in an amount of 0.3% to 0.5% by weight based onthe total dry weight of the blob 40.

As discussed above, in one embodiment, the weight of the fluid blobmixture is preferably 0.80% of the weight a molten iron/molten cast ironsample that would be contained in the sample cup 12 and the weight ofthe blob 40 is preferably 0.40% of the weight the molten iron/moltencast iron sample. As such, the weight percentages of the components ofthe fluid blob mixture and the blob 40 as compared with the total weightof the molten iron/molten cast iron sample are preferably as shown inTable 1 below:

TABLE 1 Blob Formulation wt % of molten metal sample Component FluidBlob Mixture Blob 40 Carbide stabilizer 0.96%-1.12% 0.72%-0.80% Hydrogensource 1.28%-1.44% 0.92%-1.0%  Retardant 2.96%-3.12% 2.16%-2.24% Binder2.48%-2.64% 0.06%-0.10% Dispersant 0.01%-0.04% 0.01%-0.02%

In another embodiment, the blob 40 is formed by dry compression.Specifically, the components of the blob 40 are mixed together and thenco-pressed into a pellet-like blob which is attached or adhered withinthe cavity 18 of the sample cup 12 by the use of an adhesive orrefractory cement. Alternatively, the blob may be positioned within arecess formed in a wall of the sample cup.

In such an embodiment, the pressing achieves a mechanical interlockingof the particles of the carbide stabilizer and hydrogen releasingmaterial. As such, a binder and dispersant are not necessary. Inaddition, the retardant component may be eliminated, such that releaseof the carbide stabilizer and hydrogen occurs relatively quickly. Thecarbide stabilizer is preferably present in the blob 40 in an amount of15% to 60% by weight and the hydrogen releasing material is preferablypresent in the blob 40 in an amount of 40% to 85% based on the totalweight of the blob. More preferably, the carbide stabilizer is presentin an amount of 25% to 55% by weight and the hydrogen releasing materialis present in an amount of 45% to 75% based on the total weight of theblob. Most preferably, the carbide stabilizer is present in an amount of30% to 35% by weight and the hydrogen releasing material is present inan amount of 65% to 70% based on the total weight of the blob.

Also, in such an embodiment, the weight of the carbide stabilizerpreferably constitutes 0.05% to 0.10%, and more preferably constitutes0.07% to 0.095%, of the weight of a molten iron sample that would becontained in the sample cup 12. Most preferably, the weight of thecarbide stabilizer constitutes approximately 0.074% of the weight of themolten iron sample. The weight of the hydrogen releasing materialpreferably constitutes 0.11% to 0.22%, and more preferably constitutes0.13% to 0.19%, of the weight of the molten iron sample. Mostpreferably, the weight of the hydrogen releasing material constitutesapproximately 0.14% to 0.17% of the weight of the molten iron sample.

In another embodiment, the blob 40 comprises only one essentialcomponent, namely tellurium hydroxide as a hydrogen source or hydrogenreleasing material. As such, upon contact and reaction of the blob 40with the molten iron sample, tellurium (a carbide stabilizing element),oxygen and hydrogen are all released from the tellurium hydroxide intothe molten iron sample. Preferably, the weight of the telluriumhydroxide constitutes 0.120% to 0.175% of the weight of the molten ironsample. More preferably, the weight of the tellurium hydroxideconstitutes approximately 0.150% of the weight of the molten ironsample.

The formation of various blobs 40 in accordance with preferredembodiments of the present invention will now be described in moredetail with reference to the following specific, non-limiting examples:

Examples

Five exemplary different blob mixtures were prepared by mixing variousmaterials in the proportions shown in Tables 2-6 below:

TABLE 2 Blob A Formulation Blob Component wt % (wet) wt % (dry) Carbidestabilizer 12.7% 18.4% Hydrogen source 16.8% 24.4% Retardant 37.9% 54.9%Binder 32.3% 1.9% Dispersant 0.3% 0.4%

TABLE 3 Blob B Formulation Blob Component wt % (wet) wt % (dry) Carbidestabilizer 13.0% 18.4% Hydrogen source 17.0% 24.4% Retardant 38.0% 55.3%Binder 32.0% 1.9% Dispersant — —

TABLE 4 Blob C Formulation Blob Component wt % (dry) Carbide stabilizer33.3% Hydrogen source 66.7% Retardant — Binder — Dispersant —

TABLE 5 Blob D Formulation Blob Component wt % (dry) Carbide stabilizer30.9% Hydrogen source 69.1% Retardant — Binder — Dispersant —

TABLE 6 Blob E Formulation Blob Component wt % (dry) Carbide stabilizer— Hydrogen source 100% Retardant — Binder — Dispersant —

The carbide stabilizer for Blobs A, B and C was tellurium. The hydrogensource for Blobs A, B and C was magnesium hydroxide. The hydrogen sourceof Blob D was calcium hydroxide. The hydrogen source of Blob E wastellurium hydroxide. The retardant for Blobs A and B was calcinedkaolin. The binder for Blobs A and B was 3% polyvinyl alcohol-watersolution. The dispersant for Blob A was trisodium citrate.

For Blobs A and B, the respective components of the blobs were mixedtogether to form fluid blob mixtures. Each prepared fluid blob mixturewas then dispensed into the cavity of a molten metal sample cup (i.e.,sample cup 12 as described above). The sample cup had a casting modulusof approximately 6 centimeters and a volume of approximately 37milliliters. The volume and weight of the dispensed fluid blob mixturewere approximately 0.85 milliliters and approximately 2.16 grams,respectively.

The sample cup with the dispensed fluid blob mixture therein was thenallowed to dry in ambient conditions to form a solid, dried blob 40 andto effect a final cure of the binder, which in turn adheres or bonds thedried blob 40 within the cavity 18 of the sample cup 12. The weight ofthe resulting solid, dried blob 40 was approximately 0.4% of the weightof the molten iron sample to be contained in the sample cup 12, assumingthe sample cup cavity were completely filled.

For Blobs C and D, the components of the blob were mixed together andsubsequently co-pressed to form a pellet-like Blobs C and D. For Blob E,the particles of the tellurium hydroxide were pressed together to formpellet-like Blob E. Each of the Blobs C, D and E was then attached oradhered within the cavity of a sample cup by a refractory cement. Thesample cup had a casting modulus of approximately 6 centimeters and avolume of approximately 37 milliliters.

Each of Blobs A, B, C, D and E disposed within the cavity of arespective sample cup, was then contacted with a molten iron sample. Foreach of Blobs A, B, C, D and E, the weight percentages of the respectivecomponents relative to the weight of the molten iron sample are shown inTable 7 below:

TABLE 7 Weight Percents of Blob Components Component Blob A Blob B BlobC Blob D Blob E Carbide stabilizer 0.074% 0.074% 0.091% 0.091% —Hydrogen source 0.098% 0.098% 0.182% 0.205% 0.15% Retardant 0.220%0.221% — — — Binder 0.008% 0.008% — — — Dispersant 0.002% — — — —

For Blob A, in particular, the presence of the magnesium hydroxide wasfound to enable cross-linking of the polyvinyl alcohol of the binderwithout the application of any heat treatment. While polyvinyl alcoholwould typically tend to absorb ambient moisture (and thus not besuitable for purposes of the present invention), cross-linked polyvinylalcohol exhibits sufficient moisture-resistant properties as necessaryfor the blob 40. Thus, a blob having superior moisture-resistantproperties was surprisingly found to result from the particularcombination of magnesium hydroxide and polyvinyl alcohol.

In addition, for each of the Blobs A, B and C, both hydrogen (releasedfrom the magnesium hydroxide) and tellurium were released into themolten iron sample. In addition, the magnesium released from themagnesium hydroxide was surprisingly found to be completely neutralizedupon reaction of the blob 40 with the molten iron sample. As such, thereleased magnesium did not have any contaminating effects on the molteniron or interfere with the tellurium. Instead, the released magnesiumsurprisingly permitted a complete white solidification of the molteniron.

Also, each of the Blobs A, B, C, D and E was found to be resistant tochanges in hydration levels. Specifically, each of the Blobs A, B, C, Dand E was resistant to moisture gain and moisture loss during long-termtransport and/or storage, even in extremely humid or extremely drytransport and storage conditions.

Accordingly, either no environmentally absorbed water accumulated on theBlobs A, B, C, D and E, or any such accumulation was minimal. As aresult, when each of the Blobs A, B, C, D and E was exposed to themolten metal sample, any uncontrolled boiling was eliminated or minimal.Thus, the amount of molten metal initially poured into the sample cupremained virtually unchanged during solidification of the metal. As aresult, use of the Blobs A, B, C, D and E resulted in predictablecooling/solidification times from pour to pour.

Also, each of the Blobs A, B, C, D and E did not contain any trappedmoisture, and thus was not subject to premature drying typicallyeffected due to such moisture. Thus, the composition of each blob, andspecifically the content of the hydrogen releasing material, remainsvirtually unchanged from the point of manufacture, through transport andstorage, until use.

Further, the amount of carbide stabilizer, particularly tellurium,needed to achieve complete white solidification in the blob 40 is muchless as compared with prior art coatings and blobs, as shown in Table 8below:

TABLE 8 Tellurium Content Fe wt % Te Te wt (theoretical fill)*(theoretical fill) Prior Art Blob 0.388 343.0 0.113% Blob 40 0.200 269.40.074% *The “theoretical” values refer to a state in which the volume ofthe sample cup 12 is completely filled with molten iron.

Thus, blobs of the present invention and detection devices includingblobs of the present invention may be used over a broad range of pouringtemperatures, pouring conditions, and storage and transport conditionswith excellent results.

It will be appreciated by those skilled in the art that changes could bemade to the embodiments described above without departing from the broadinventive concept thereof. It is understood, therefore, that thisinvention is not limited to the particular embodiments disclosed, but itis intended to cover modifications within the spirit and scope of thepresent invention as defined by the appended claims.

I claim:
 1. A method of detecting phase change temperatures of a sample of molten iron or molten cast iron, the method comprising the steps of: providing a detection device including a temperature sensor and a sample cup with a cavity configured to receive a sample of molten iron or molten cast iron; arranging a blob in the cavity, the blob comprising a carbide stabilizer and magnesium hydroxide as a hydrogen releasing material; depositing a sample of molten iron or molten cast iron into the cavity, the blob reacting with the molten iron or molten cast iron sample upon contact therewith, such that hydrogen is released from the magnesium hydroxide into the molten iron or molten cast iron sample; and allowing the molten iron or molten cast iron sample to solidify while simultaneously measuring phase change temperatures of the solidifying sample.
 2. The method according to claim 1, wherein the blob further comprises a binder.
 3. The method according to claim 2, wherein the binder is a 3% polyvinyl alcohol-water solution.
 4. The method according to claim 3, wherein the 3% polyvinyl alcohol-water solution comprises 1% to 4% by weight based on a total weight of the blob.
 5. The method according to claim 1, wherein the blob comprises 0.35% to 0.45% by weight based on a total weight of a sample of molten metal.
 6. The method according to claim 1, wherein the blob is resistant to changes in its hydration level during transport and storage of the blob.
 7. The method according to claim 1, wherein the blob further comprises a retardant which resists reaction of the blob upon contact with molten metal.
 8. The method according to claim 1, wherein the carbide stabilizer comprises 7% to 37% by weight based on a total weight of the blob.
 9. The method according to claim 1, wherein the carbide stabilizer is tellurium.
 10. The method according to claim 9, wherein the blob comprises the tellurium in an amount of 15% to 60% by weight based on a total weight of the blob and the magnesium hydroxide in an amount of 40% to 85% by weight based on the total weight of the blob, the blob being resistant to moisture gain and moisture loss during transport and storage.
 11. The method according to claim 9, wherein the tellurium is present in an amount of 0.05% to 0.10% by weight based on a total weight of a molten iron sample and the magnesium hydroxide is present in an amount of 0.11% to 0.22% by weight based on the total weight of the molten iron sample.
 12. The method according to claim 1, wherein the magnesium hydroxide comprises 15% to 54% by weight based on a total weight of the blob.
 13. A method of manufacturing a blob for use in detecting phase change temperatures of a sample of molten metal, the method comprising: forming a fluid blob mixture comprising a carbide stabilizer and magnesium hydroxide as a hydrogen releasing material; providing a detection device including a sample cup with a cavity configured to receive a sample of molten metal; depositing the fluid blob mixture into the cavity; and drying the fluid blob mixture to form a blob.
 14. The method of claim 13, wherein the carbide stabilizer comprises 5% to 25% by weight based on a total weight of the fluid blob mixture and comprises 7% to 37% by weight based on a total weight of the blob.
 15. The method of claim 13, wherein the magnesium hydroxide comprises 10% to 37% by weight based on a total weight of the fluid blob mixture and comprises 15% to 54% by weight based on a total weight of the blob. 